Structural, elastic, and electronic properties of newly discovered Li2PtSi3 superconductor: Effect of transition metals

First-principles calculations within the density functional theory (DFT) with GGA-PBE exchange-correlation scheme have been employed to predict the structural, the elastic and the electronic properties of newly discovered lithium silicide superconductor, Li2PtSi3, for the first time. All the theoretical results are compared with those calculated recently for isostructural Li2IrSi3. The present study sheds light on the effect of replacement of transition metal element Ir with Pt on different mechanical, electronic, and superconducting properties. The effect of spin-orbit coupling on electronic band structure was found to be insignificant for Li2PtSi3. The difference in superconducting transition temperatures of Li2PtSi3 and Li2IrSi3 arises primarily due to the difference in electronic energy density of states at the Fermi level. Somewhat reduced Debye temperature in Li2PtSi3 plays a minor role. We have discussed the implications of the theoretical results in details in this study.Comment: Submitted for publicatio

Molybdenum compounds bearing pymS (pyrimidine-2-thiolato) and tertiary phosphine ligands

741-746In this paper we have reported mono- and dinuclear molybdenum compounds containing doubly bridging pymS (pyrimidine-2-thiolato) and P(Fu)3 {(Fu = (2-furyl)phosphine)} or P(OMe)3 (trimethyl phosphite). One-pot reaction between [Mo(CO)3(NCMe)3] and pymSH (pyrimidine-2-thiol) in the presence of P(Fu)3 in THF at 50 °C gives the previously reported eight coordinate compound [Mo(к2-pymS)4] (1) in 17% yield and two new compounds [Mo(CO)4(P(Fu)3)2] (2) and [Mo2(CO)4(μ-к2-pymS)2(P(Fu)3)2] (3) in 51 and 15% yields, respectively. A similar reaction involving P(OMe)3 furnishes two mononuclear compounds [Mo(CO)2(κ2-pyS)2(P(OMe)3)] (4) and [Mo(CO)4(P(OMe)3)2] (5) in 20 and 35% yields, respectively. Compounds 2 and 4 are characterized by single-crystal X-ray diffraction analysis in addition to IR, 1H NMR and 31P{1H} NMR spectroscopic methods

New MAX phase superconductor Ti2GeC: A first-principles study

This is the first DFT-based first-principles prediction of the detailed optical and thermodynamic properties, including Vickers hardness and Fermi surface of 211 MAX phase Ti2GeC for which superconductivity (Tc~ 9.5 K) was reported very recently. The calculated structural properties are in excellent agreement with experiments. Our results on elastic parameters indicate a slight elastic anisotropy and brittleness of the compound. The chemical bonding is seen to be a combination of covalent, ionic and metallic nature. The rather stronger covalent bonding is responsible for its high Vickers hardness of 11.6 GPa. The investigated Fermi surface is formed mainly by the low-dispersive bands, which should be responsible for the presence of superconductivity in Ti2GeC. All the optical properties are evaluated and analyzed for two different polarization directions of incident photon. The temperature and pressure dependence of primitive cell volume, thermal expansion coefficient, specific heats, bulk modulus, and Debye temperature of Ti2GeC are derived from the quasi-harmonic Debye model with phononic effect and the various implications are discussed in details

Structural, elastic, electronic and optical properties of Cu3MTe4 (M = Nb, Ta) sulvanites: An ab initio study

The elastic, electronic, and optical properties of Cu3MTe4 (M = Nb, Ta) are investigated for the first time using the density-functional formalism. The optimized crystal structure is obtained and the lattice parameters are compared with available experimental data. Different elastic moduli are calculated. The Born criteria for mechanicalstability are found to be fulfilled from the estimated values of the elastic moduli, Cij . The band structure and the electronic energy density of states (EDOS) are also determined. The band structure calculations show semiconducting behavior for both the compounds. The theoretically calculated values of the band gaps are found to be strongly dependent on the nature of the functional representing the exchange correlations. Technologically significant optical parameters (e.g., dielectric function, refractive index, absorption coefficient, optical conductivity, reflectivity, and loss function) have been determined. Important conclusions are drawn based on the theoretical findings